Rainfall and temperature predict bird colouration, international study finds
An international study led by a Monash University ornithologist
has found variation in rainfall and temperature can affect the colours of
birds. The study provides a new framework that can be used to understand how
future changes in climate will affect animals.
The research published today in
the journal Ecology Letters examines colour variation across nearly 6000
species of passerines birds, the largest group of birds.
The research team, which included ornithologists from Monash
University, Massey University, and the Max Planck Institute of Ornithology
undertook a global analysis of bird plumage colour variation.
They observed darker coloured birds occurring in regions
with high rainfall and colder temperatures.
“Nearly 200 years ago, Constantin Gloger noticed that
animals living in tropical regions tended to be more pigmented,” said lead
study author Dr Kaspar Delhey, from the Monash School of Biological Sciences.
“His observations, and that of others, were synthesised
into’ Gloger’s rule’, which predicts that animals should be darker in warmer
and wetter regions, possibly because darker animals are better camouflaged in
shady habitats, such as in tropical rainforests.”
But Gloger’s rule partly conflicts with another rule
explaining colour variation in animals: Bogert’s rule, which predicts darker
animals in colder regions, because darker colours absorb more solar radiation
which helps with thermoregulation.
The global scale of the recent study allowed the researchers
not only to comprehensively test both rules, but also to determine why some
groups of birds sometimes don’t seem to follow them.
“We found quite a bit of variation across different regions
of the world in how closely birds followed the rules” said Dr Delhey.
“For example in South America there seems to be little correlation
between coloration and temperature and we wondered why that was so.
“It turns out that both rules can interfere with each other.
In particular, precipitation–which has a very strong effect– can overwhelm the
weaker temperature effect.”
This happens when climate ranges from cold-and-dry to
hot-and-humid. In such places the lightening effect of temperature is swamped
by the darkening effect of rainfall.
On the other hand, when climate varies from hot-and-dry to
cold-and-wet, the rules reinforce each other and their effects become stronger.
Thus, the type of climatic gradient determines whether both rules work together
or against each other and this can explain why certain groups of animals
seemingly fail to follow the rules.
“Understanding how animal form and function is shaped by
climate is particularly relevant today, given the ongoing threat of climate
change, which predicts future increases in temperature and changes in
precipitation patterns,” said Dr Delhey.
“Geographic variation in coloration, such as described by
Gloger’s and Bogert’s rules, can therefore provide hints on how animals have
adapted to past variation in climate and how they will fare in the future. “
For further information or to arrange an interview with
Dr Kaspar Delhey, contact:
Silvia Dropulich Marketing, Media and
Communications Manager, Science
T: +61 3 9902 4513 M: +61 (0) 0435138743
E: silvia.dropulich@monash.edu
-ENDS-
MEDIA ENQUIRIES
Media
Monash University
T: +61 3 9903 4840 E: media@monash.edu
For more Monash media stories, visit our news and events site
Looking for a Monash expert? Search Expertline.